Huub Vikings are 50-60 cm long and shoot up to 30 fpe - if you can find one. Another short one would be a Marauder pistol with a bullpup kit, they are also about 50 cm long and can do well over 20 fpe. Kalibrgun is introducing a Capybara, a very interesting looking semi-auto pup that has the same features as Colibri. When getting a bullpup you should consider if you want the cocking lever at your armpit or if it's more convenient to have it in front for easy shooting.
Viking Mk2 .177/.22 bullpup, BSA Scorpion SE .177, BSA Scorpion .25 100M gun, BSA Scorpion .224 100fpe 100M gun,
Evanix Blizzard .257/.357 200M BR, Evanix Sniper X2 .45 at 270 fpe